Carpal tunnel syndrome is a common problem that affects the hand and wrist. This condition, or syndrome, has become the focus of much attention in the last few years due to suggestions that it may be linked to certain occupations that require repetitive use of the hands, such as typing. While certain occupations may experience more problems with carpal tunnel syndrome, many people develop this condition regardless of their occupation.
Particularly, carpal tunnel syndrome (CTS) is a condition that results when the median nerve of the hand does not function properly. Usually, this occurs because there is too much pressure on the median nerve that extends into the wrist through an opening called the carpal tunnel. The median nerve extends into the hand to receive sensation from the thumb, index finger, long finger, and half of the ring finger. The median nerve also provides a branch to the muscles of the thumb (i.e. the thenar muscles).
The carpal tunnel is an opening into the hand that is made up of the bones of the wrist (i.e. the carpals) on the bottom and the transverse carpal ligament on the top. The median nerve and the flexor tendons extend through the carpal tunnel into the hand. The median nerve lies just under the transverse carpal ligament (TCL). A material called the tenosynovium covers the flexor tendons. The tenosynovium is slippery and thus allows the tendons to glide against each other as they move. Any condition that causes irritation or inflammation of the tendons can result in swelling and/or thickening of the tenosynovium. As the tenosynovium begins to swell and/or thicken, pressure begins to increase in the carpal tunnel. This is because the bones and ligaments that form the carpel tunnel are fixed in size and thus are not able to stretch to accommodate the swelling. Increased pressure in the carpel tunnel begins to squeeze the median nerve against the transverse carpal ligament, since the median nerve is the softest structure in the carpal tunnel. Eventually, the pressure reaches a point where the median nerve can no longer function normally. This manifests itself as pain and numbness in the hand.
There are many conditions that can result in irritation and inflammation of the tenosynovium, and eventually cause carpal tunnel syndrome. Different types of arthritis can cause inflammation of the tenosynovium directly. A fracture of the wrist bones may later cause carpal tunnel syndrome if the healed fragments result in abnormal irritation on the flexor tendons. Particularly, anything that causes abnormal pressure on the median nerve will result in the symptoms of carpal tunnel syndrome.
In the early stages of carpal tunnel syndrome, non-operative treatments are typically used. One such non-operative treatment is the use of a brace. The brace keeps the wrist in a neutral position. When the wrist is in a neutral position, the carpal tunnel is as large as it can be so the median nerve has as much room as possible.
Another non-operative treatment that tries to reduce the symptoms of carpal tunnel syndrome is the use of anti-inflammatory medications to help control swelling of the tenosynovium. Anti-inflammatory medications include over the counter medications such as ibuprofen and aspirin, as well as high doses of vitamin B-6. Injections of cortisone into the carpal tunnel may also be used in order to decrease swelling of the tenosynovium and thereby give temporary relief of symptoms.
If the non-operative treatments fail to control the symptoms of carpal tunnel syndrome, surgery may be required to reduce the pressure on the median nerve. There are essentially three surgical techniques designed to relieve pressure on the median nerve. The first and most common surgical procedure is the traditional open incision technique. The second surgical procedure is known as the mini-open. The third procedure is an endoscopic technique.
The traditional open incision technique requires a 2 to 2½ inch incision to be made in the palm of the hand. A structure called the palmer fascia is then incised in order to reach the transverse carpal ligament. The transverse carpal ligament is then cut while making sure that the median nerve is out of the way and protected. The cut or incision may be slight (small incised amount) or drastic (e.g. as in a full carpal tunnel release (CTR) procedure). Pressure on the median nerve is relieved after cutting of the transverse carpal ligament. The incised skin is then sutured. The transverse carpal ligament remains open and the gap is slowly filled by scar tissue.
Major drawbacks to the standard, open incision technique are the slowness of recovery and the size of the resulting scar. Often the 2 inch palm side scar remains sensitive to direct pressure for approximately six to eight weeks. For a working patient, this scar sensitivity may preclude return to normal work activities. Generally, the greater the invasiveness of the remedial methodology, the longer the recovery time is for the patient.
The mini-open technique utilizes a 1 to 1½ cm incision proximate the transverse carpal ligament. Various instruments are placed through the incision and utilized to cut the TCL from underneath as appropriate.
In the endoscopic carpal tunnel release technique, a small horizontal incision is made at the wrist and an arthroscope is introduced underneath the transverse carpal ligament. A small knife or blade, attached to the end of the arthroscope, is utilized to incise or cut the transverse carpal ligament. Again, cutting through the transverse carpal ligament alleviates the compression on the median nerve. While the endoscopic carpal tunnel release technique is less invasive than the traditional, and is typically accomplished on an outpatient basis, it is nonetheless an invasive procedure that requires time to heal. Because the incision is not retracted to provide an open view, a camera probe and light are inserted through small openings placed in the arm or hand to provide the surgeon with a view of the anatomical structure of the surgical site. However, known endoscopic imaging methods may not provide adequate visualization of the TCL and its surrounding structure so some surgeons prefer an open incision technique.
Moreover, with current invasive techniques, the surgeon must rely on his/her own expertise for determining, not only the location and orientation of the initial incision on the palm of the hand, but also in deciding where the transverse carpel ligament should be dissected. The place of dissection is critical because while it is desired to split the transverse carpal ligament, the surgeon must not lacerate any major branch of the median or ulnar nerves.
Although current complication rates are low (approximately 3-4%), inadvertent laceration of a nerve (either fully or partially) can have catastrophic effects on the functionality of the patient's hand. The risk of hand impairment may cause patients suffering from carpal tunnel syndrome to forego surgical remedies of the malady.
In view of the above, a therapeutic technique for performing carpal tunnel release that reduces the risk of median or ulnar nerve laceration is desirable.
Methodologies for encouraging endoscopic procedures are needed to reduce the trauma and recovery time associated with more invasive surgical procedures.